net: dpaa2-eth: don't use -ENOTSUPP error code

dpaa2_eth_setup_dpni() is called from the probe path and
dpaa2_eth_set_link_ksettings() is propagated to user space.

include/linux/errno.h says that ENOTSUPP is "Defined for the NFSv3
protocol". Conventional wisdom has it to not use it in networking
drivers. Replace it with -EOPNOTSUPP.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>